As textile substrates age, their color tends to fade or yellow due to exposure to light, air, soil, and natural degradation of the fibers that comprise the substrates. Thus, the purpose of hueing agents is generally to visually brighten these textile substrates and counteract the fading and yellowing of the substrates. Typically, hueing agents may be found in laundry detergents, fabric softeners, or rinse aids and are therefore applied to textile substrates during the laundering process. However, it is important that hueing agents function to visually brighten treated textile substrates without causing undesirable staining of the textile substrates. Cellulosic substrates, in particular, tend to exhibit a yellow hue after exposure to light, air, and/or soiling. This yellowness is often difficult to reverse by normal laundering procedures. As a result, there exists a need for improved hueing agents which are capable of eliminating the yellowness exhibited by ageing cellulosic substrates. By utilizing such improved hueing agents, the life of the textile substrates, such as clothing articles, table linens, etc., may be extended. Unfortunately, current hueing agents either do not provide a hueing benefit after a single treatment cycle and/or they build up to an undesirable level, thus overhueing the treated situs over multiple treatment cycles.
The hueing agents disclosed herein and the laundry care compositions comprising same offer advantages over previous efforts in this area, as, unlike previous thiophene azo hueing agents, the present hueing agents comprise a formally charged moiety that allows such hueing agents to provide enhanced deposition, removal and hue angle when used in compositions such as laundry care compositions. In addition to the enhanced deposition, removal and hue angle, the present hueing agents offer improved stability in wash environments that contain bleaching agents, for example bleach boosters. While not being bound by theory, Applicants believe that such enhanced stability is, at least in part, due to the improved partitioning behavior of such hueing agents. The aforementioned benefits are offered over a range of fabric types. In short, Applicants recognized the source of the current hueing deficiencies and herein provide the solution to such problem. The hueing compounds disclosed herein also absorb light at a wavelength appropriate to visually neutralize the yellowness of substrates, including textile substrates. These compounds function ideally as hueing agents for substrates, including textile substrates, and may be incorporated into laundry care compositions for use by consumers.